1. Field of the Invention
The present invention relates generally to an apparatus for, and a method of, embedding and extracting digital information, as well as a medium having a program for carrying out the method recorded thereon. More particularly, the present invention generally relates to an apparatus for, and a method of, embedding, in order to protect the copyright of digital data, digital data such as copyright information (hereinafter referred to as digital information) in an image signal, and extracting the embedded digital information, as well as a medium having a program for carrying out the method recorded thereon.
2. Description of the Background Art
In recent years, information utilizing the Internet has been extensively provided. Particularly, WWW (World Wide Web) has been frequently utilized as an information transmitting and receiving service in which images, voices, and so forth are integrated.
However, digital information, such as an image which is open to the public on a network of the Internet, can be easily copied by many and unspecified users. Therefore, some problems have arisen. For example, an image whose copyright is owned by a third person is secondarily utilized by making unauthorized copying thereof without the permission of the copyright owner. Further, also in expanding the business on the Internet using image-based contents, measures to prevent the unauthorized copying have been a problem. Therefore, the establishment of a technique for protecting the copyright of an image signal has been demanded.
An example of the measures conventionally known is an electronic watermark technique. The digital watermarking is a technique for embedding digital information in image data in a form that cannot be perceived by a human being.
Examples of the conventional electronic watermark technique include an electronic watermark technique using discrete wavelet transform described in an article entitled xe2x80x9cEmbedding a Signature to Picture under Wavelet Transformationxe2x80x9d by Matsui, Onishi, Nakamura et al. (Journal of The Institute of Electronics, Information and Communication Engineers D-II VOL. J79-D-II, No. 6, pp. 1017 to 1024, June 1996) (hereinafter referred to as a technique by Matsui et al.).
The technique by Matsui et al. will be described with reference to FIGS. 33 to 35.
Description is now made of band division by discrete wavelet transform processing.
FIG. 33 is a block diagram showing an example of the structure of a conventional band dividing device 11 for division into three hierarchies. In FIG. 33, the conventional band dividing device 11 comprises first to third band dividing filters 100, 200 and 300 having the same structure. Each of the first to third band dividing filters 100, 200 and 300 divides a received image into four frequency bands, and calculates wavelet transform coefficients (hereinafter merely referred to as transform coefficients) for each of the frequency bands.
It is also possible to obtain transform coefficients even by sub-band division which is equivalent to the band division by discrete wavelet transform, which is not described herein.
The band dividing device 11 inputs a digitized image signal 71 into the first band dividing filter 100. The first band dividing filter 100 divides the image signal 71 into signals in four bands, i.e., an LL1 signal, an LH1 signal, an HL1 signal and an HH1 signal (hereinafter generically referred to as a first hierarchical signal) on the basis of parameters of its horizontal and vertical frequency components. The second band dividing filter 200 receives the LL1 signal in the lowest band in the first hierarchical signal, and further divides the LL1 signal into an LL2 signal, an LH2 signal, an HL2 signal and an HH2 signal in four bands (hereinafter generically referred to as a second hierarchical signal). The third band dividing filter 300 receives the LL2 signal in the lowest band in the second hierarchical signal, and further divides the LL2 signal into an LL3 signal, an LH3 signal, an HL3 signal and an HH3 signal in four bands (hereinafter generically referred to as a third hierarchical signal).
FIG. 34 is a block diagram showing an example of the structure of the first band dividing filter 100. In FIG. 34, the first band dividing filter 100 comprises first to third two-band division portions 101 to 103. The first to third two-band division portions 101 to 103 respectively comprise one-dimensional low-pass filters (LPF) 111 to 113, one-dimensional high-pass filters (HPF) 121 to 123, and sub-samplers 131 to 133 and 141 to 143 for thinning a signal at a ratio of 2:1.
The first two-band division portion 101 receives the image signal 71, and subjects the signal to low-pass filtering and high-pass filtering with respect to its horizontal component by the LPF 111 and the HPF 121, respectively, to output two signals. The signals obtained by the low-pass filtering and the high-pass filtering are respectively thinned at a ratio of 2:1 using the sub-samplers 131 and 141, and are then outputted to the subsequent stage. The second two-band division portion 102 receives the signal from the sub-sampler 131, and filters the signal with respect to its vertical component by the LPF 112 and the BPF 122, respectively, thins the signal at a ratio of 2:1 using the sub-samplers 132 and 142, and then outputs two signals, i. e., an LL signal and an LH signal. On the other hand, the third two-band division portion 103 receives the signal from the sub-sampler 141, and respectively filters the signal with respect to its vertical component by the LPF 113 and the HPF 123, thins the signal at a ratio of 2:1 using the sub-samplers 133 and 143, and then outputs two signals, i.e., an HL signal and an HH signal.
Consequently, four signals, i.e., the LL1 signal which is low in both its horizontal and vertical components, the LH1 signal which is low in its horizontal component and is high in its vertical component, the HL1 signal which is high in its horizontal component and is low in its vertical component, and the HH1 signal which is high in both its horizontal and vertical components, that is, transform coefficients are outputted from the first band-dividing filter 100.
The second and third band dividing filters 200 and 300 also respectively subject received signals to the same processing as described above.
As a result of the band division processing by the first to third band dividing filters 100, 200 and 300, the image signal 71 is divided into 10 band signals, i.e., an LL3 signal, an LH3 signal, an HL3 signal, an HH3 signal, an LH2 signal, an HL2 signal, an HH2 signal, an LH1 signal, an HL1 signal and an HH1 signal.
FIG. 35 is a diagram showing representation of the signals by a two-dimensional frequency region.
In FIG. 35, the vertical axis represents a vertical frequency component, which increases as it is directed downward, and the horizontal axis represents a horizontal frequency component, which increases as it is directed rightward. Each of regions in FIG. 35 is data serving as one image, and the area ratio of the regions coincides with the ratio of the respective numbers of data in the band signals. That is, in a case where the number of data in the LL3 signal, the LH3 signal, the HL3 signal and the HH3 signal which are the third hierarchical signal is taken as one, the number of data in the LH2 signal, the HL2 signal and the HH2 signal which are the second hierarchical signal is four, and the number of data in the LH1 signal, the HL1 signal and the HH1 signal which are the first hierarchical signal is 16. Consequently, with respect to one data at the upper left of the LL3 signal, for example, one data at the upper left of each of the LH3 signal, the HL3 signal and the HH3 signal, four data, which are square, at the upper left of each of the LH2 signal, the HL2 signal and the HH2 signal, 16 data, which are square, at the upper left of each of the LH1 signal, the HL1 signal and the HH1 signal represent the same pixel on an original image (portions painted in black in FIG. 35).
Description is now made of a method of embedding digital information after the above-mentioned band division by discrete wavelet transform. The embedding method itself described below is a technique well-known by those skilled in the art. Matsui et al. realize digital watermarking by combining the discrete wavelet transform and the conventional embedding method.
The conventional embedding method utilizes visual characteristics of a human being who easily overlooks noise in a high frequency region and easily detects noise in a low frequency region. That is, in an image signal, energy is concentrated in its low frequency component. Therefore, in output components in the discrete wavelet transform, an LL signal representing a low frequency component of the image signal is an important band component. On the other hand, three types of signals, i.e., an LH signal, an HL signal and an HH signal representing high frequency components, shown in multi-resolution representation (MRR), of the image signal are not so important band components.
With respect to each of the MRR components, i.e., the LH signal, the HL signal and the HH signal, which are not so important, the logical value of the low-order bit (least significant bit (LSB) if possible) of a wavelet transform coefficient, which is not zero out of wavelet transform coefficients in the MRk component, is transformed in accordance with the value of a bit, in digital information, to be embedded on the basis of previously determined regularity, to perform digital watermarking.
In the technique by Matsui et al., the digital information is embedded in only the MRR components which are high frequency components of an image calculated by the discrete wavelet transform and the low-order bits thereof which hardly affect the change in the image. Therefore, the degradation of the quality of an image reconstructed by the signal in which the digital information has been embedded is so slight as not to be perceived with the eyes of a human being.
In the case of display and distribution, for example, on a network, the signals in the respective frequency bands which have been subjected to the above-mentioned embedding processing are synthesized by a band synthesizing device (in short, performing processing reverse to the discrete wavelet transform), to reconstruct an image signal. Further, in order to extract the embedded digital information from the reconstructed image signal, the discrete wavelet transform is performed to extract the logical values transformed in the embedding processing.
In the above-mentioned technique by Matsui et al., however, the digital information is embedded in the MRR components which are high frequency components of the image, the following problems remain.
(1) By frequency-transforming the image in which the digital information has been embedded, and then rewriting and cutting the high frequency components of the image, the embedded digital information can be removed relatively simply.
(2) Even by subjecting the image in which the digital information has been embedded to low-pass filtering, the high frequency components of the image are reduced, so that the embedded digital information is lost.
(3) Furthermore, in image communication, for example, the image is transmitted upon being compressed. In the case, the high frequency components of the transform coefficients of the image are generally coarsely quantized to perform irreversible compression, so that the effect on the high frequency components of the image is increased. That is, the respective lower-order bits of the transform coefficients in the MRR components of the image are significantly changed, so that the embedded digital information cannot be correctly extracted.
Therefore, an object of the present invention is to provide an apparatus for, and a method of, embedding and extracting digital information, in which it is possible to reliably extract, by embedding digital information in not only transform coefficients having high frequency components of an image, but also transform coefficients having low frequency components, which degrade the quality of the image at the time of extracting the embedded digital information and further embedding the digital information only in transform coefficients having not the high frequency components but the low frequency components, the embedded digital information, without losing the information against the above-mentioned attack from an unauthorized user, and the quality of the image is hardly degraded at the time of extracting the embedded digital information, and a medium having a program for carrying out the method recorded thereon.
In order to attain the above-mentioned object, the present invention has the following features.
A first aspect is directed to a digital information embedding apparatus for embedding inherent digital information in a digital image signal, comprising:
band division means for dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
block division means for dividing the lowest frequency band out of the plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size;
quantization means for calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q (Q is an integer of not less than one), to calculate a quantization value;
signal replacement means for replacing for each of the blocks, on the basis of the quantization value and the value of the digital information to be embedded which correspond to the block, the quantization value;
mean difference addition means for subjecting for each of the blocks the replaced quantization value to inverse linear quantization using the quantization step-size Q to calculate a mean value Mxe2x80x2, and adding a difference DM (=Mxe2x80x2xe2x88x92M) between the mean value Mxe2x80x2 and the mean value M to all the transform coefficients in the block;
mean calculation means for calculating a mean value LM of the transform coefficients in the lowest frequency band after the addition of the difference DM; and
band synthesis means for reconstructing a digital image signal in which the digital information has been embedded using the lowest frequency band after the addition of the difference DM and the other frequency bands.
As described in the foregoing, according to the first aspect, the digital information is embedded in the transform coefficients in the lowest frequency band using either the discrete wavelet transform, or the sub-band division. Consequently, it is possible to prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A second aspect is directed to a digital information embedding apparatus for embedding inherent digital information in a digital image signal, comprising:
orthogonal transform means for dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined, and subjecting, for each of the blocks, the block to orthogonal transform, to calculate transform coefficients;
block selection means for further classifying the plurality of blocks obtained by the division into groups each comprising one or two or more blocks in accordance with a previously determined number of blocks;
quantization means for extracting, for each of the blocks belonging to each of the groups, the transform coefficient having the lowest frequency component (hereinafter referred to as a DC component) out of the transform coefficients in the block and calculating a mean value M of the respective DC components in the blocks, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q (Q is an integer of not less than one), to calculate a quantization value;
signal replacement means for replacing for each of the groups, on the basis of the quantization value and the value of the digital information to be embedded which correspond to the group, the quantization value;
mean difference addition means for subjecting for each of the groups the replaced quantization value to inverse linear quantization using the quantization step-size Q to calculate a mean value Mxe2x80x2, and adding a difference DM (=Mxe2x80x2xe2x88x92M) between the mean value Mxe2x80x2 and the mean value M to all the DC components in the blocks belonging to the group;
inverse orthogonal transform means for subjecting the plurality of blocks after the addition of the difference DM to inverse orthogonal transform, to reconstruct a digital image signal in which the digital information has been embedded; and
mean calculation means for calculating a mean value LM of the amplitude values of the pixels in the reconstructed digital image signal.
As described in the foregoing, according to the second aspect, the digital information is embedded only in the lowest frequency component using the orthogonal transform. Consequently, it is possible to prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A third aspect is characterized in that in the second aspect, the orthogonal transform means performs signal transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform.
As described in the foregoing, according to the third aspect, the typical system of the signal transformation performed by the orthogonal transform means in the second aspect is specified.
A fourth aspect is directed to a digital information embedding apparatus for embedding inherent digital information in a digital image signal, comprising:
block selection means for dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined;
quantization means for calculating for each of the blocks a mean value M of the pixels composing the block, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q (Q is an integer of not less than one), to calculate a quantization value;
signal replacement means for replacing for each of the blocks, on the basis of the quantization value and the value of the digital information to be embedded which correspond to the block, the quantization value;
mean difference addition means for subjecting for each of the blocks the replaced quantization value to inverse linear quantization using the quantization step-size Q to calculate a mean value Mxe2x80x2, and adding a difference DM (=Mxe2x80x2xe2x88x92M) between the mean value Mxe2x80x2 and the mean value M to all the pixels composing the block; and
mean calculation means for calculating a mean value LM of the amplitude values of the pixels in the digital image signal after the addition of the difference DM.
As described in the foregoing, according to the fourth aspect, the digital information is embedded in the mean value of the pixels composing the block, that is, the lowest frequency component. Consequently, it is possible to prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A fifth aspect is characterized in that the signal replacement means of the first aspect replaces the quantization value with an odd value closest to the value of (MQ) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
A sixth aspect is characterized in that in the second aspect,
the signal replacement means replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
A seventh aspect is characterized in that in the third aspect,
the signal replacement means replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
An eighth aspect is characterized in that in the fourth aspect,
the signal replacement means replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
As described in the foregoing, according to the fifth to eighth aspects, the quantization value is replaced with the odd or even value closest to the value of (M/Q) on the basis of the logical value of each of the bits composing the digital information in the first to fourth aspects. Consequently, it is possible to reduce the degradation of the image at the time of extracting the embedded digital information, and it is difficult for a third person to detect the embedded digital information.
A ninth aspect is directed to a digital information extracting apparatus for extracting inherent digital information embedded by a particular apparatus in transform coefficients in the lowest frequency band obtained by dividing a digital image signal using either discrete wavelet transform or sub-band division, wherein the digital image signal outputted by the particular apparatus and a quantization step-size are inputted, comprising:
band division means for dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
block division means for dividing the lowest frequency band out of the plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size;
quantization means for calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using the previously determined quantization step-size Q, to calculate a quantization value; and
digital information judgment means for judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the ninth aspect, the logical value of the embedded digital information is judged by the results of extracting the transform coefficients which have been embedded in the lowest frequency band which is hardly affected by data destruction in high frequency bands, and calculating the quantization value of the mean value of the transform coefficients in each of the blocks in the low frequency band using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A tenth aspect is directed to a digital information extracting apparatus for extracting inherent digital information embedded by a particular apparatus in transform coefficients in the lowest frequency band obtained by dividing a digital image signal using either discrete wavelet transform or sub-band division, wherein the digital image signal outputted by the particular apparatus, a quantization step-size, and a mean value LM of the transform coefficients in the lowest frequency band at the time of output are inputted, comprising:
band division means for dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
mean difference subtraction means for calculating a mean value LMxe2x80x2 of the transform coefficients in the lowest frequency band out of the plurality of frequency bands obtained by the division, and subtracting a difference DM (=LMxe2x80x2xe2x88x92LM) between the mean value LMxe2x80x2 and the mean value LM from all the transform coefficients in the lowest frequency band;
block division means for dividing the lowest frequency band after the subtraction of the difference DL into a plurality of blocks in accordance with a previously determined block size;
quantization means for calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using the quantization step-size Q, to calculate a quantization value; and
digital information judgment means for judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the tenth aspect, the logical value of the embedded digital information is judged by the results of calculating, with respect to the lowest frequency band including the transform coefficients whose mean value is corrected using the mean values LMxe2x80x2 and LM even when it is changed by image processing such as irreversible compression, the quantization value of the mean value of the transform coefficients in each of the blocks in the low frequency band using a previously determined method. Consequently, more accurate digital information can be extracted without being affected by an attack from an unauthorized user.
An eleventh aspect is directed to a digital information extracting apparatus for extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by subjecting a digital image signal to signal transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform, then dividing the digital image signal into blocks, and subjecting each of the blocks to orthogonal transform, wherein the digital image signal outputted by the particular apparatus and a quantization step-size are inputted, comprising:
orthogonal transform means for dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined, and subjecting, for each of the blocks, the block to orthogonal transform, to calculate transform coefficients;
block selection means for further classifying the plurality of blocks obtained by the division into groups each comprising one or two or more blocks in accordance with a previously determined number of blocks;
quantization means for calculating for each of the groups a mean value of the respective transform coefficients having the lowest frequency components in the blocks belonging to the group, and subjecting the mean value to linear quantization using the previously determined quantization step-size, to calculate a quantization value; and
digital information judgment means for judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the eleventh aspect, the logical value of the embedded digital information is judged by the results of extracting the transform coefficient which has been embedded in the lowest frequency component which is hardly affected by data destruction in high frequency bands, and calculating the quantization value of the mean value of the respective transform coefficients having the lowest frequency components in the plurality of blocks using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A twelfth aspect is directed to a digital information extracting apparatus for extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by subjecting a digital image signal to signal transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform, then dividing the digital image signal into blocks, and subjecting each of the blocks to orthogonal transform, wherein the digital image signal outputted by the particular apparatus, a quantization step-size, and a mean value LM of the amplitude values of pixels in the digital image signal at the time of output are inputted, comprising:
mean difference subtraction means for calculating a mean value LMxe2x80x2 of the amplitude values of the pixels in the digital image signal at the time of input, and subtracting a difference DM (=LMxe2x80x2xe2x88x92LM) between the mean value LMxe2x80x2 and the mean value LM from the values of all the pixels in the digital image signal;
orthogonal transform means for dividing the digital image signal after the subtraction of the difference DL into a plurality of blocks each composed of a plurality of pixels previously determined, and subjecting, for each of the blocks, the block to orthogonal transform, to calculate transform coefficients;
block selection means for further classifying the plurality of blocks obtained by the division into groups each comprising one or two or more blocks in accordance with a previously determined number of blocks;
quantization means for calculating for each of the groups a mean value of the respective transform coefficients having the lowest frequency components in the blocks belonging to the group, and subjecting the mean value to linear quantization using the previously determined quantization step-size, to calculate a quantization value; and
digital information judgment means for judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the twelfth aspect, the logical value of the embedded digital information is judged by the results of calculating, with respect to the lowest frequency component, in the digital image signal, including the transform coefficients whose mean value is corrected using the mean values LMxe2x80x2 and LM of the amplitude values of the pixels in the digital image signal even when it is changed by image processing such as irreversible compression, the quantization value of the mean value of the respective transform coefficients having the lowest frequency components in the plurality of blocks using a previously determined method. Consequently, more accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A thirteenth aspect is directed to a digital information extracting apparatus for extracting inherent digital information embedded by a particular apparatus in a mean value of pixels composing each of blocks obtained by dividing a digital image signal, wherein the digital image signal outputted by the particular apparatus and a quantization step-size are inputted, comprising:
block selection means for dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined;
quantization means for calculating for each of the blocks a mean value of the pixels composing the block, and subjecting the mean value to linear quantization using the quantization step-size, to calculate a quantization value; and
digital information judgment means for judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the thirteenth aspect, the logical value of the embedded digital information is judged by the results of extracting the mean value of the pixels composing the block which is hardly affected by data destruction in high frequency bands, and calculating the quantization value of the mean value using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A fourteenth aspect is directed to a digital information extracting apparatus for extracting inherent digital information embedded by a particular apparatus in a mean value of pixels composing each of blocks obtained by dividing a digital image signal, wherein the digital image signal outputted by the particular apparatus, a quantization step-size, and a mean value LM of the amplitude values of the pixels in the digital image signal at the time of output are inputted, comprising:
mean difference subtraction means for calculating a mean value LMxe2x80x2 of the amplitude values of the pixels in the digital image signal at the time of input, and subtracting a difference DL (=LMxe2x80x2xe2x88x92LM) between the mean value LMxe2x80x2 and the mean value LM from the values of all the pixels in the digital image signal;
block selection means for dividing the digital image signal after the subtraction of the difference DL into a plurality of blocks each composed of a plurality of pixels previously determined;
quantization means for calculating a mean value of the pixels composing each of the blocks obtained by the division, and subjecting the mean value to linear quantization using the quantization step-size, to calculate a quantization value; and
digital information judgment means for judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the fourteenth aspect, the logical value of the embedded digital information is judged by the results of calculating, with respect to the digital image signal including blocks each composed of the pixels whose mean value is corrected using the mean values LMxe2x80x2 and LM of the amplitude values of the pixels in the digital image signal even when it is changed by image processing such as irreversible compression, the quantization value of the mean value of the pixels composing the block using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A fifteenth aspect is directed to a digital information embedding apparatus for embedding inherent digital information in a digital image signal, comprising:
band division means for dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
map information generation means for generating, with respect to each of the transform coefficients included in the one or two frequency bands out of the plurality of frequency bands obtained by the division, map information storing a true/false value based on decision whether or not all the absolute amplitude values of the transform coefficient and the other transform coefficients in the same space representation region in the same direction of division as the one or two frequency bands are not more than a previously determined set value;
signal replacement means for replacing all of the transform coefficient and the other transform coefficients which correspond to the position where the true/false value of the map information is true with a previously determined transform value on the basis of the value of the digital information to be embedded in the transform coefficients; and
band synthesis means for synthesizing the plurality of transform coefficients after the replacement, to reconstruct a digital image signal.
As described in the foregoing, according to the fifteenth aspect, the digital information is embedded in the frequency signal over a plurality of hierarchies using either the discrete wavelet transform or the sub-band division. Consequently, it is possible to prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A sixteenth aspect is characterized in that in the fifteenth aspect,
the transform value is set to integers xc2x1K which are not more than the set value, and
the signal replacement means replaces the transform coefficient and the other transform coefficients with the transform value +K when each of bits composing the digital information takes a logical value 1, while replacing the transform coefficients with the transform value xe2x88x92K when the bit takes a logical value 0.
As described in the foregoing, according to the sixteenth aspect, the transform coefficient whose absolute amplitude value is not more than the set value is replaced with the transform values xc2x1K which are set to not more than the set value. Consequently, it is possible to reduce the effect on the degradation of the image at the time of extracting the embedded digital information, and it is difficult for a third person to detect the embedded digital information.
A seventeenth aspect is characterized in that in the fifteenth aspect,
the map information generation means generates the map information with respect to the transform coefficients included in at least one or both of the frequency band which is low in its horizontal component and is high in its vertical component and the frequency band which is high in its horizontal component and is low in its vertical component.
An eighteenth aspect is characterized in that in the sixteenth aspect,
the map information generation means generates the map information with respect to the transform coefficients included in at least one or both of the frequency band which is low in its horizontal component and is high in its vertical component and the frequency band which is high in its horizontal component and is low in its vertical component.
As described in the foregoing, according to the seventeenth and eighteenth aspects, the digital information is embedded in the frequency signal having the lower frequency component in the fifteenth and sixteenth aspects. Consequently, it is possible to further prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A nineteenth aspect is directed to a digital information embedding apparatus for embedding inherent digital information in a digital image signal, comprising:
band division means for dividing the digital image signal into transfer coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
map information generation means for generating, with respect to each of the transform coefficients included in the one or two frequency bands out of the plurality of frequency bands obtained by the division, map information storing a true/false value based on decision whether or not the absolute amplitude value of the transform coefficient is included between upper-limit and lower-limit threshold values which are previously determined;
signal replacement means for replacing the transform coefficient corresponding to the position where the true/false value of the map information is true with a previously determined transform value on the basis of the sign of the transform coefficient and the value of the digital information to be embedded in the transform coefficient; and
band synthesis means for synthesizing the plurality of transform coefficients after the replacement, to reconstruct a digital image signal.
As described in the foregoing, according to the nineteenth aspect, the digital information is embedded only in the transform coefficients in a deep hierarchical signal which is hardly affected using the discrete wavelet transform or the sub-band division. Consequently, it is possible to further prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A twentieth aspect is directed to a digital information embedding apparatus for embedding inherent digital information in a digital image signal, comprising:
orthogonal transform means for dividing the digital image signal into a plurality of block signals of a previously determined size, and subjecting, for each of the block signals, the block signal to orthogonal transform, to calculate transform coefficients;
map information generation means for generating, with respect to each of the transform coefficients included in the one or two block signals out of the plurality of block signals obtained by the division, map information storing a true/false value based on decision whether or not the absolute amplitude value of the transform coefficient is included between upper-limit and lower-limit threshold values which are previously determined;
signal replacement means for replacing the transform coefficient corresponding to the position where the true/false value of the map information is true with a previously determined transform value on the basis of the sign of the transform coefficient and the value of the digital information to be embedded in the transform coefficient; and
inverse orthogonal transform means for subjecting the plurality of transform coefficients after the replacement to inverse orthogonal transform, to reconstruct a digital image signal.
As described in the foregoing, according to the twentieth aspect, the digital information is embedded only in the transform coefficients in a deep hierarchical signal which is hardly affected using the orthogonal transform. Consequently, it is possible to further prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A twenty-first aspect is characterized in that in the twentieth aspect,
the orthogonal transform means performs frequency transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform.
As described in the foregoing, according to the twenty-first aspect, the typical system of the frequency transformation performed by the orthogonal transform means in the twentieth aspect is specified.
A twenty-second aspect is characterized in that in the nineteenth aspect, the transform value is set to integers xc2x1A and xc2x1B between the upper-limit and lower-limit threshold values, and
the signal replacement means replaces the transform coefficient with the transform value +A when each of bits composing the digital information takes a logical value 1 and the sign of the transform coefficient is positive, with the transform value xe2x88x92A when the bit takes a logical value 1 and the sign of the transform coefficient is negative, with the transform value +B when the bit takes a logical value 0 and the sign of the transform coefficient is positive, and with the transform value xe2x88x92B when the bit takes a logical value 0 and the sign of the transform coefficient is negative.
A twenty-third aspect is characterized in that in the twentieth aspect,
the transform value is set to integers xc2x1A and xc2x1B between the upper-limit and lower-limit threshold values, and
the signal replacement means replaces the transform coefficient with the transform value +A when each of bits composing the digital information takes a logical value 1 and the sign of the transform coefficient is positive, with the transform value xe2x88x92A when the bit takes a logical value 1 and the sign of the transform coefficient is negative, with the transform value +B when the bit takes a logical value 0 and the sign of the transform coefficient is positive, and with the transform value xe2x88x92B when the bit takes a logical value 0 and the sign of the transform coefficient is negative.
A twenty-fourth aspect is characterized in that in the twenty-first aspect,
the transform value is set to integers xc2x1A and xc2x1B between the upper-limit and lower-limit threshold values, and
the signal replacement means replaces the transform coefficient with the transform value +A when each of bits composing the digital information takes a logical value 1 and the sign of the transform coefficient is positive, with the transform value xe2x88x92A when the bit takes a logical value 1 and the sign of the transform coefficient is negative, with the transform value +B when the bit takes a logical value 0 and the sign of the transform coefficient is positive, and with the transform value xe2x88x92B when the bit takes a logical value 0 and the sign of the transform coefficient is negative.
As described in the foregoing, according to the twenty-second to twenty-fourth aspects, the transform coefficient whose absolute amplitude value is within the threshold range is transformed into and replaced with a value within the threshold range considering the sign of the transform coefficient. Consequently, it is possible to reduce the effect on the degradation of the image at the time of extracting the embedded digital information, and it is difficult for a third person to detect the embedded digital information.
A twenty-fifth aspect is characterized in that in the nineteenth aspect,
the map information generation means generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A twenty-sixth aspect is characterized in that in the twentieth aspect,
the map information generation means generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A twenty-seventh aspect is characterized in that in the twenty-first aspect,
the map information generation means generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A twenty-eighth aspect is characterized in that in the twenty-second aspect,
the map information generation means generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A twenty-ninth aspect is characterized in that in the twenty-third aspect,
the map information generation means generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A thirtieth aspect is characterized in that in the twenty-fourth aspect,
the map information generation means generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
As described in the foregoing, according to the twenty-fifth to thirtieth aspects, the digital information is embedded in the frequency signal having the lower frequency component in the nineteenth to twenty-fourth aspects. Consequently, it is possible to further prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A thirty-first aspect is directed to a digital information extracting apparatus for extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by dividing a digital image signal using either discrete wavelet transform or sub-band division, wherein the digital image signal outputted by the particular apparatus and map information representing the position where the digital information is embedded are inputted, comprising:
band division means for dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
map information analysis means for extracting, on the basis of the map information, the transform coefficient corresponding to the position where a true/false value of the map information is true and the other transform coefficients in the same space representation region in the same direction of division as the frequency band including the transform coefficient;
coefficient calculation means for calculating a total value of the transform coefficients included in the one or two or more frequency bands out of the transform coefficient and the other transform coefficients which are extracted; and
digital information judgment means for judging the sign of the total value, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the thirty-first aspect, the logical value of the embedded digital information is judged by the results of extracting the transform coefficients which have been embedded in the low frequency band which is hardly affected by data destruction in high frequency bands, and calculating the total value of the transform coefficients using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A thirty-second aspect is directed to a digital information extracting apparatus for extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by dividing a digital image signal using either discrete wavelet transform or sub-band division, wherein the digital image signal outputted by the particular apparatus, map information representing the position where the digital information is embedded, and information representing a transform value to be embedded are inputted, comprising:
band division means for dividing the image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
map information analysis means for extracting, on the basis of the map information, the transform coefficient corresponding to the position where a true/false value of the map information is true;
error calculation means for calculating an absolute error between the extracted transform coefficient and the transform value; and
digital information judgment means for judging the absolute error, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the thirty-second aspect, the logical value of the embedded digital information is judged by the results of extracting the transform coefficient which has been embedded in a deep hierarchical signal which is not affected by data destruction in high frequency bands, and calculating and judging the absolute error between the transform coefficient and the transform value using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A thirty-third aspect is directed to a digital information extracting apparatus for extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by subjecting a digital image signal to frequency transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform, then dividing the digital image signal into blocks, and subjecting each of the blocks to orthogonal transform, wherein the digital image signal outputted by the particular apparatus, map information representing the position where the digital information is embedded, and information representing a transform value to be embedded are inputted, comprising:
orthogonal transform means for dividing the digital image signal into a plurality of block signals of a previously determined size, and subjecting, for each of the block signals, the block signal to orthogonal transform, to calculate transform coefficients;
map information analysis means for extracting, on the basis of the map information, the transform coefficient corresponding to the position where a true/false value of the map information is true;
error calculation means for calculating an absolute error between the extracted transform coefficient and the transform value; and
digital information judgment means for judging the absolute error, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the thirty-third aspect, the logical value of the embedded digital information is judged by the results of extracting the transform coefficient which has been embedded in a deep hierarchical signal which is not affected by data destruction in high frequency bands and calculating and judging the absolute error between the transform coefficient and the transform value using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A thirty-fourth aspect is directed to a digital information embedding method of embedding inherent digital information in a digital image signal, comprising the steps of:
dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
dividing the lowest frequency band out of the plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size;
calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q (Q is an integer of not less than one), to calculate a quantization value;
replacing for each of the blocks, on the basis of the quantization value and the value of the digital information to be embedded which correspond to the block, the quantization value;
subjecting for each of the blocks the replaced quantization value to inverse linear quantization using the quantization step-size Q to calculate a mean value Mxe2x80x2, and adding a difference DM (=Mxe2x80x2xe2x88x92M) between the mean value Mxe2x80x2 and the mean value M to all the transform coefficients in the block;
calculating a mean value LM of the transform coefficients in the lowest frequency band after the addition of the difference DM; and
reconstructing a digital image signal in which the digital information has been embedded using the lowest frequency band after the addition of the difference DM and the other frequency bands.
As described in the foregoing, according to the thirty-fourth aspect, the digital information is embedded in the transform coefficients in the lowest frequency band using either the discrete wavelet transform, or the sub-band division. Consequently, it is possible to prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A thirty-fifth aspect is directed to a digital information embedding method of embedding inherent digital information in a digital image signal, comprising the steps of:
dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined, and subjecting, for each of the blocks, the block to orthogonal transform, to calculate transform coefficients;
further classifying the plurality of blocks obtained by the division into groups each comprising one or two or more blocks in accordance with a previously determined number of blocks;
extracting, for each of blocks belonging to each of the groups, the transform coefficient having the lowest frequency component (hereinafter referred to as a DC component) out of the transform coefficients in the block and calculating a mean value M of the respective DC components in the blocks, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q (Q is an integer of not less than one), to calculate a quantization value;
replacing for each of the groups, on the basis of the quantization value and the value of the digital information to be embedded which correspond to the group, the quantization value;
subjecting for each of the groups the replaced quantization value to inverse linear quantization using the quantization step-size Q to calculate a mean value Mxe2x80x2, and adding a difference DM (=Mxe2x80x2xe2x88x92M) between the mean value Mxe2x80x2 and the mean value M to all the respective DC components in the blocks belonging to the group;
subjecting the plurality of blocks after the addition of the difference DM to inverse orthogonal transform, to reconstruct a digital image signal in which the digital information has been embedded; and
calculating a mean value LM of the amplitude values of the pixels in the reconstructed digital image signal.
As described in the foregoing, according to the thirty-fifth aspect, the digital information is embedded only in the lowest frequency component using the orthogonal transform. Consequently, it is possible to prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A thirty-sixth aspect is characterized in that in the thirty-fifth aspect,
the step of respectively calculating the transform coefficients performs signal transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform.
As described in the foregoing, according to the thirty-sixth aspect, the typical system of the signal transformation performed in the calculating step in the thirty-fifth aspect is specified.
A thirty-seventh aspect is directed to a digital information embedding method of embedding inherent digital information in a digit al image signal, comprising the steps of:
dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined;
calculating for each of the blocks a mean value M of the pixels composing the block, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q (Q is an integer of not less than one), to calculate a quantization value;
replacing for each of the blocks, on the basis of the quantization value and the value of the digital information to be embedded which correspond to the block, the quantization value;
subjecting for each of the blocks the replaced quantization value to inverse linear quantization using the quantization step-size Q to calculate a mean value MI, and adding a difference DM (=Mxe2x80x2xe2x88x92M) between the mean value Mxe2x80x2 and the mean value M to all the pixels composing the block; and
calculating a mean value LM of the amplitude values of the pixels in the digital image signal after the addition of the difference DM.
As described in the foregoing, according to the thirty-seventh aspect, the digital information is embedded in the mean value of the pixels composing the block, that is, the lowest frequency component. Consequently, it is possible to prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A thirty-eighth aspect is characterized in that the step of replacing the quantization value of the thirty-fourth aspect replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
A thirty-ninth aspect is characterized in that in the thirty-fifth aspect,
the step of replacing the quantization value replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
A fortieth aspect is characterized in that in the thirty-sixth aspect,
the step of replacing the quantization value replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
A forty-first aspect is characterized in that in the thirty-seventh aspect,
the step of replacing the quantization value replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
As described in the foregoing, according to the thirty-eighth to forty-first aspects, the quantization value is replaced with an odd or even value closest to the value of (M/Q) on the basis of the logical value of each of the bits composing the digital information in the thirty-fourth to thirty-seventh aspects. Consequently, it is possible to reduce the effect on the degradation of the image at the time of extracting the embedded digital information, and it is difficult for a third person to detect the embedded digital information.
A forty-second aspect is directed to a digital information extracting method of extracting inherent digital information embedded by a particular apparatus in transform coefficients in the lowest frequency band obtained by dividing a digital image signal using either discrete wavelet transform or sub-band division, wherein the digital image signal outputted by the particular apparatus and a quantization step-size are inputted, comprising the steps of:
dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
dividing the lowest frequency band out of the plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size;
calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using the previously determined quantization step-size Q, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the forty-second aspect, the logical value of the embedded digital information is judged by the results of extracting the transform coefficients which have been embedded in the lowest frequency band which is hardly affected by data destruction in high frequency bands, and calculating the quantization value of the mean value of the transform coefficients in each of the blocks in the lowest frequency band using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A forty-third aspect is directed to a digital information extracting method of extracting inherent digital information embedded by a particular apparatus in transform coefficients in the lowest frequency band obtained by dividing a digital image signal using either discrete wavelet transform or sub-band division, wherein the digital image signal outputted by the particular apparatus, a quantization step-size, and a mean value LM of the transform coefficients in the lowest frequency band at the time of output are inputted, comprising the steps of:
dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
calculating a mean value LMxe2x80x2 of the transform coefficients in the lowest frequency band out of the plurality of frequency bands obtained by the division, and subtracting a difference DM (=LMxe2x80x2xe2x88x92LM) between the mean value LMxe2x80x2 and the mean value LM from all the transform coefficients in the lowest frequency band;
dividing the lowest frequency band after the subtraction of the difference DL into a plurality of blocks in accordance with a previously determined block size;
calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using the quantization step-size Q, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the forty-third aspect, the logical value of the embedded digital information is judged by the results of calculating, with respect to the lowest frequency band including the transform coefficients whose mean value is corrected using the mean values LMxe2x80x2 and LM even when it is changed by image processing such as irreversible compression, the quantization value of the mean value of the transform coefficients in each of the blocks in the lowest frequency band using a previously determined method. Consequently, more accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A forty-fourth aspect is directed to a digital information extracting method of extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by subjecting a digital image signal to frequency transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform, then dividing the digital image signal into blocks, and subjecting each of the blocks to orthogonal transform, wherein the digital image signal outputted by the particular apparatus and a quantization step-size are inputted, comprising the steps of:
dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined, and subjecting, for each of the blocks, the block to orthogonal transform, to calculate transform coefficients;
further classifying the plurality of blocks obtained by the division into groups each comprising one or two or more blocks in accordance with a previously determined number of blocks;
calculating for each of the groups a mean value of the respective transform coefficients having the lowest frequency components in the blocks belonging to the group, and subjecting the mean value to linear quantization using the previously determined quantization step-size, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the forty-fourth aspect, the logical value of the embedded digital information is judged by the results of extracting the transform coefficient which has been embedded in the lowest frequency component which is hardly affected by data destruction in high frequency bands, and calculating the quantization value of the mean value of the respective transform coefficients having the lowest frequency components in the plurality of blocks using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A forty-fifth aspect is directed to a digital information extracting method of extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by subjecting a digital image signal to signal transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform, then dividing the digital image signal into blocks, and subjecting each of the blocks to orthogonal transform, wherein the digital image signal outputted by the particular apparatus, a quantization step-size, and a mean value LM of the amplitude values of pixels in the digital image signal at the time of output are inputted, comprising the steps of:
calculating a mean value LMxe2x80x2 of the amplitude values of the pixels in the digital image signal at the time of input, and subtracting a difference DM (=LMxe2x80x2xe2x88x92LM) between the mean value LMxe2x80x2 and the mean value LM from the values of all the pixels in the digital image signal;
dividing the digital image signal after the subtraction of the difference DL into a plurality of blocks each composed of the plurality of pixels previously determined, and subjecting, for each of the blocks, the block to orthogonal transform, to calculate transform coefficients;
further classifying the plurality of blocks obtained by the division into groups each comprising one or two or more blocks in accordance with a previously determined number of blocks;
calculating for each of the groups a mean value of the respective transform coefficients having the lowest frequency components in the blocks belonging to the group, and subjecting the mean value to linear quantization using the previously determined quantization step-size, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the forty-fifth aspect, the logical value of the embedded digital information is judged by the results of calculating, with respect to the lowest frequency component, in the digital image signal, including the transform coefficients whose mean value is corrected using the mean values LMxe2x80x2 and LM of the amplitude values of the pixels in the digital image signal even when it is changed by image processing such as irreversible compression, the quantization value of the mean value of the respective transform coefficients having the lowest frequency components in the plurality of blocks using a previously determined method. Consequently, more accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A forty-sixth aspect is directed to a digital information extracting method of extracting inherent digital information embedded by a particular apparatus in a mean value of pixels composing each of blocks obtained by dividing a digital image signal, wherein the digital image signal outputted by the particular apparatus and a quantization step-size are inputted, comprising the steps of:
dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined;
calculating for each of the blocks a mean value of the pixels composing the block, and subjecting the mean value to linear quantization using the quantization step-size, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the forty-sixth aspect, the logical value of the embedded digital information is judged by the results of extracting the mean value of the pixels composing the block which is hardly affected by data destruction in high frequency bands, and calculating the quantization value of the mean value using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A forty-seventh aspect is directed to a digital information extracting method of extracting inherent digital information embedded by a particular apparatus in a mean value of pixels composing each of blocks obtained by dividing a digital image signal, wherein the digital image signal outputted by the particular apparatus, a quantization step-size, and a mean value LM of the amplitude values of the pixels in the digital image signal at the time of output are inputted, comprising the steps of:
calculating a mean value LMxe2x80x2 of the amplitude values of the pixels in the digital image signal at the time of input, and subtracting a difference DL (=LMxe2x80x2xe2x88x92LM) between the mean value LMxe2x80x2 and the mean value LM from the values of all the pixels in the digital image signal;
dividing the digital image signal after the subtraction of the difference DL into a plurality of blocks each composed of a plurality of pixels previously determined;
calculating a mean value of the pixels composing each of the blocks obtained by the division, and subjecting the mean value to linear quantization using the quantization step-size, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the forty-seventh aspect, the logical value of the embedded digital information is judged by the results of calculating, with respect to the digital image signal including the blocks each composed of pixels whose mean value is corrected using the mean values LMxe2x80x2 and LM of the amplitude values of the pixels in the digital image signal even when it is changed by image processing such as irreversible compression, the quantization value of the mean value of the pixels composing the block using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A forty-eighth aspect is directed to a digital information embedding method of embedding inherent digital information in a digital image signal, comprising the steps of:
dividing the digital image signal into a plurality of frequency bands to obtain transform coefficients using either discrete wavelet transform or sub-band division;
generating, with respect to each of the transform coefficients included in the one or two frequency bands out of the plurality of frequency bands obtained by the division, map information storing a true/false value based on decision whether or not all the absolute amplitude values of the transform coefficient and the other transform coefficients in the same space representation region in the same direction of division as the one or two frequency bands are not more than a previously determined set value;
replacing all of the transform coefficient and the other transform coefficients which correspond to the position where the true/false value of the map information is true with a previously determined transform value on the basis of the value of the digital information to be embedded in the transform coefficients; and
synthesizing the plurality of transform coefficients after the replacement, to reconstruct a digital image signal.
As described in the foregoing, according to the forty-eighth aspect, the digital information is embedded in a frequency signal over a plurality of hierarchies using either the discrete wavelet transform or the sub-band division. Consequently, it is possible to prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A forty-ninth aspect is characterized in that in the forty-eighth aspect,
the transform value is set to integers xc2x1K which are not more than the set value, and
the replacing step replaces the transform coefficient and the other transform coefficients with the transform value xc2x1K when each of bits composing the digital information takes a logical value 1, while replacing the transform coefficients with the transform value xe2x88x92K when the bit takes a logical value 0.
As described in the foregoing, according to the forty-ninth aspect, the transform coefficient whose absolute amplitude value is not more than the set value is replaced with the transform values xc2x1K which are set to not more than the set value. Consequently, it is possible to reduce the effect on the degradation of the image at the time of extracting the embedded digital information, and it is difficult for a third person to detect the embedded digital information.
A fiftieth aspect is characterized in that in the forty-eighth aspect,
the generating step generates the map information with respect to the transform coefficients included in at least one or both of the frequency band which is low in its horizontal component and is high in its vertical component and the frequency band which is high in its horizontal component and is low in its vertical component.
A fifty-first aspect is characterized in that in the forty-ninth aspect,
the generating step generates the map information with respect to the transform coefficients included in at least one or both of the frequency band which is low in its horizontal component and is high in its vertical component and the frequency band which is high in its horizontal component and is low in its vertical component.
As described in the foregoing, according to the fiftieth and fifty-first aspects, the digital information is embedded in the frequency signal having the lower frequency component in the forty-eighth and forty-ninth aspects. Consequently, it is possible to prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A fifty-second aspect is directed to a digital information embedding method of embedding inherent digital information in a digital image signal, comprising the steps of:
dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
generating, with respect to each of the transform coefficients included in the one or two frequency bands out of the plurality of frequency bands obtained by the division, map information storing a true/false value based on decision whether or not the absolute amplitude value of the transform coefficient is included between upper-limit and lower-limit threshold values which are previously determined;
replacing the transform coefficient corresponding to the position where the true/false value of the map information is true with a previously determined transform value on the basis of the sign of the transform coefficient and the value of the digital information to be embedded in the transform coefficient; and
synthesizing the plurality of transform coefficients after the replacement, to reconstruct a digital image signal.
As described in the foregoing, according to the fifty-second aspect, the digital information is embedded only in the transform coefficients in a deep hierarchical signal which is hardly affected using either the discrete wavelet transform or the sub-band division. Consequently, it is possible to further prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A fifty-third aspect is directed to a digital information embedding method of embedding inherent digital information in a digital image signal, comprising the steps of:
dividing the digital image signal into a plurality of block signals of a previously determined size, and subjecting, for each of the block signals, the block signal to orthogonal transform, to calculate transform coefficients;
generating, with respect to each of the transform coefficients included in the one or two block signals out of the plurality of block signals obtained by the division, map information storing a true/false value based on decision whether or not the absolute amplitude value of the transform coefficient is included between upper-limit and lower-limit threshold values which are previously determined;
replacing the transform coefficient corresponding to the position where the true/false value of the map information is true with a previously determined transform value on the basis of the sign of the transform coefficient and the value of the digital information to be embedded in the transform coefficient; and
subjecting the plurality of transform coefficients after the replacement to inverse orthogonal transform, to reconstruct a digital image signal.
As described in the foregoing, according to the fifty-third aspect, the digital information is embedded only in the transform coefficients in a deep hierarchical signal which is hardly affected using the orthogonal transform. Consequently, it is possible to further prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A fifty-fourth aspect is characterized in that in the fifty-third aspect,
the calculating step performs frequency transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform.
As described in the foregoing, according to the fifty-fourth aspect, the typical system of the frequency transformation performed by the orthogonal transform means in the fifty-third aspect is specified.
A fifty-fifth aspect is characterized in that in the fifty-second aspect,
the transform value is set to integers xc2x1A and xc2x1B between the upper-limit and lower-limit threshold values, and
the replacing step replaces the transform coefficient with the transform value +A when each of bits composing the digital information takes a logical value 1 and the sign of the transform coefficient is positive, with the transform value xe2x88x92A when the bit takes a logical value 1 and the sign of the transform coefficient is negative, with the transform value +B when the bit takes a logical value 0 and the sign of the transform coefficient is positive, and with the transform value xe2x88x92B when the bit takes a logical value 0 and the sign of the transform coefficient is negative.
A fifty-sixth aspect is characterized in that in the fifty-third aspect,
the transform value is set to integers xc2x1A and xc2x1B between the upper-limit and lower-limit threshold values, and
the replacing step replaces the transform coefficient with the transform value +A when each of bits composing the digital information takes a logical value 1 and the sign of the transform coefficient is positive, with the transform value xe2x88x92A when the bit takes a logical value 1 and the sign of the transform coefficient is negative, with the transform value +B when the bit takes a logical value 0 and the sign of the transform coefficient is positive, and with the transform value xe2x88x92B when the bit takes a logical value 0 and the sign of the transform coefficient is negative.
A fifty-seventh aspect is characterized in that in the fifty-fourth aspect, the transform value is set to integers xc2x1A and xc2x1B between the upper-limit and lower-limit threshold values, and
the replacing step replaces the transform coefficient with the transform value +A when each of bits composing the digital information takes a logical value 1 and the sign of the transform coefficient is positive, with the transform value xe2x88x92A when the bit takes a logical value 1 and the sign of the transform coefficient is negative, with the transform value +B when the bit takes a logical value 0 and the sign of the transform coefficient is positive, and with the transform value xe2x88x92B when the bit takes a logical value 0 and the sign of the transform coefficient is negative.
As described in the foregoing, according to the fifty-fifth to fifty-seventh aspects, the transform coefficient whose absolute amplitude value is within the threshold range is transformed into and replaced with a value within the threshold range considering the sign of the transform coefficient. Consequently, it is possible to reduce the effect on the degradation of the image at the time of extracting the embedded digital information, and it is difficult for a third person to detect the embedded digital information.
A fifty-eighth aspect is characterized in that in the fifty-second aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A fifty-ninth aspect is characterized in that in the fifty-third aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A sixtieth aspect is characterized in that in the fifty-fourth aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A sixty-first aspect is characterized in that in the fifth-fifth aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A sixty-second aspect is characterized in that in the fifty-sixth aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A sixty-third aspect is characterized in that in the fifty-seventh aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
As described in the foregoing, according to the fifty-eighth to sixty-third aspects, the digital information is embedded in the frequency signal having the lower frequency component in the fifty-second to fifty-seventh aspects. Consequently, it is possible to further prevent the embedded digital information from being lost against an attack for unauthorized utilization from a third person.
A sixty-fourth aspect is directed to a digital information extracting method of extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by dividing a digital image signal using either discrete wavelet transform or sub-band division, wherein the digital image signal outputted by the particular apparatus and map information representing the position where the digital information is embedded are inputted, comprising the steps of:
dividing the digital image signal into a plurality of frequency bands to obtain transform coefficients using either discrete wavelet transform or sub-band division;
extracting, on the basis of the map information, the transform coefficient corresponding to the position where a true/false value of the map information is true and the other transform coefficients in the same space representation region in the same direction of division as the frequency band including the transform coefficient;
calculating a total value of the transform coefficients included in the one or two or more frequency bands out of the transform coefficient and the other transform coefficients which are extracted; and
judging the sign of the total value, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the sixty-fourth aspect, the logical value of the embedded digital information is judged by the results of extracting the transform coefficients which have been embedded in the low frequency band which is hardly affected by data destruction in high frequency bands, and calculating the total value of the transform coefficients using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A sixty-fifth aspect is directed to a digital information extracting method of extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by dividing a digital image signal using either discrete wavelet transform or sub-band division, wherein the digital image signal outputted by the particular apparatus, map information representing the position where the digital information is embedded, and information representing a transform value to be embedded are inputted, comprising the steps of:
dividing the image signal into a plurality of frequency bands to obtain transform coefficients using either discrete wavelet transform or sub-band division;
extracting, on the basis of the map information, the transform coefficient corresponding to the position where a true/false value of the map information is true;
calculating an absolute error between the extracted transform coefficient and the transform value; and
judging the absolute error, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the sixty-fifth aspect, the logical value of the embedded digital information is judged by the results of extracting the transform coefficient which has been embedded in a deep hierarchical signal which is not affected by data destruction in high frequency bands, and calculating and judging the absolute error between the transform coefficient and the transform value using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A sixty-sixth aspect is directed to a digital information extracting method of extracting inherent digital information embedded by a particular apparatus in transform coefficients obtained by subjecting a digital image signal to frequency transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform, then dividing the digital image signal into blocks, and subjecting each of the blocks to orthogonal transform, wherein the digital image signal outputted by the particular apparatus, map information representing the position where the digital information is embedded, and information representing a transform value to be embedded are inputted, comprising the steps of:
dividing the digital image signal into a plurality of block signals of a previously determined size, and subjecting, for each of the block signals, the block signal to orthogonal transform, to calculate transform coefficients;
extracting, on the basis of the map information, the transform coefficient corresponding to the position where a true/false value of the map information is true;
calculating an absolute error between the extracted transform coefficient and the transform value; and
judging the absolute error, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, according to the sixty-sixth aspect, the logical value of the embedded digital information is judged by the results of extracting, even with respect to a particular digital image signal which has already been subjected to frequency transformation, the transform coefficient which has been embedded in a deep hierarchical signal which is not affected by data destruction in high frequency bands and calculating and judging the absolute error between the transform coefficient and the transform value using a previously determined method. Consequently, accurate digital information can be extracted without being affected by an attack from an unauthorized user.
A sixty-seventh aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising the steps of:
dividing a digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
dividing the lowest frequency band out of the plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size;
calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q (Q is an integer of not less than one), to calculate a quantization value; replacing for each of the blocks, on the basis of the quantization value and the value of the digital information to be embedded which correspond to the block, the quantization value; subjecting for each of the blocks the replaced quantization value to inverse linear quantization using the quantization step-size Q to calculate a mean value Mxe2x80x2, and adding a difference DM (=Mxe2x80x2xe2x88x92M) between the mean value Mxe2x80x2 and the mean value M to all the transform coefficients in the block; calculating a mean value LM of the transform coefficients in the lowest frequency band after the addition of the difference DM; and reconstructing a digital image signal in which the digital information has been embedded using the lowest frequency band after the addition of the difference DM and the other frequency bands.
A sixty-eighth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising the steps of
dividing a digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined, and subjecting, for each of the blocks, the block to orthogonal transform, to calculate transform coefficients;
further classifying the plurality of blocks obtained by the division into groups each comprising one or two or more blocks in accordance with a previously determined number of blocks;
extracting, for each of the blocks belonging to each of the groups, the transform coefficient having the lowest frequency component (hereinafter referred to as a DC component) out of the transform coefficients in the block and calculating a mean value M of the respective DC components in the blocks, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q (Q is an integer of not less than one), to calculate a quantization value;
replacing for each of the groups, on the basis of the quantization value and the value of the digital information to be embedded which correspond to the group, the quantization value;
subjecting for each of the groups the replaced quantization value to inverse linear quantization using the quantization step-size Q to calculate a mean value Mxe2x80x2, and adding a difference DM (=Mxe2x80x2xe2x88x92M) between the mean value Mxe2x80x2 and the mean value M to all the DC components in the blocks belonging to the group; subjecting the plurality of blocks after the addition of the difference DM to inverse orthogonal transform, to reconstruct a digital image signal in which the digital information has been embedded; and
calculating a mean value LM of the amplitude values of the pixels in the reconstructed digital image signal.
A sixty-ninth aspect is characterized in that in the sixty-eighth aspect,
the step of respectively calculating the transform coefficients performs signal transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform.
A seventieth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising the steps of:
dividing a digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined;
calculating for each of the blocks a mean value M of the pixels composing the block, and subjecting the mean value M to linear quantization using a previously determined quantization step-size Q (Q is an integer of not less than one), to calculate a quantization value;
replacing for each of the blocks, on the basis of the quantization value and the value of the digital information to be embedded which correspond to the block, the quantization value;
subjecting for each of the blocks the replaced quantization value to inverse linear quantization using the quantization step-size Q to calculate a mean value Mxe2x80x2, and adding a difference DM (=Mxe2x80x2xe2x88x92M) between the mean value Mxe2x80x2 and the mean value M to all the pixels composing the block; and
calculating a mean value LM of the amplitude values of the pixels in the digital image signal after the addition of the difference DM.
A seventy-first aspect is characterized in that the step of replacing the quantization value of the sixty-seventh aspect replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
A seventy-second aspect is characterized in that in the sixty-eighth aspect,
the step of replacing the quantization value replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
A seventy-third aspect is characterized in that in the sixty-ninth aspect,
the step of replacing the quantization value replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
A seventy-fourth aspect is characterized in that in the seventieth aspect,
the step of replacing the quantization value replaces the quantization value with an odd value closest to the value of (M/Q) when each of bits composing the digital information takes a logical value 1, while replacing the quantization value with an even value closest to the value of (M/Q) when the bit takes a logical value 0.
A seventy-fifth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising, with respect to a digital image signal having inherent digital information embedded by a particular apparatus in transform coefficients in the lowest frequency band obtained by dividing the digital image signal using either discrete wavelet transform or sub-band division, with using a quantization step-size outputted by the particular apparatus, the steps of:
dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
dividing the lowest frequency band out of the plurality of frequency bands obtained by the division into a plurality of blocks in accordance with a previously determined block size;
calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using the previously determined quantization step-size, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
A seventy-sixth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising, with respect to a digital image signal having inherent digital information embedded by a particular apparatus in transform coefficients in the lowest frequency band obtained by dividing the digital image signal using either discrete wavelet transform or sub-band division, and with a quantization step-size outputted by the particular apparatus and a mean value LM of the transform coefficients in the lowest frequency band at the time of output, the steps of:
dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
calculating a mean value LMxe2x80x2 of the transform coefficients in the lowest frequency band out of the plurality of frequency bands obtained by the division, and subtracting a difference DM (=LMxe2x80x2xe2x88x92LM) between the mean value LMxe2x80x2 and the mean value LM from all the transform coefficients in the lowest frequency band;
dividing the lowest frequency band after the subtraction of the difference DL into a plurality of blocks in accordance with a previously determined block size; calculating for each of the blocks a mean value M of the transform coefficients in the block, and subjecting the mean value M to linear quantization using the quantization step-size Q, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
A seventy-seventh aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising, with respect to a digital image signal having inherent digital information embedded by a particular apparatus in transform coefficients obtained by subjecting the digital image signal to frequency transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform, then dividing the digital image signal into blocks, and subjecting each of the blocks to orthogonal transform, and with using a quantization step-size outputted by the particular apparatus, the steps of:
dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined, and subjecting, for each of the blocks, the block to orthogonal transform, to calculate transform coefficients;
further classifying the plurality of blocks obtained by the division into groups each comprising one or two or more blocks in accordance with a previously determined number of blocks;
calculating for each of the groups a mean value of the respective transform coefficients having the lowest frequency components in the blocks belonging to the group, and subjecting the mean value to linear quantization using the previously determined quantization step-size, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
A seventy-eighth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising, with respect to a digital image signal having inherent digital information embedded by a particular apparatus in transform coefficients obtained by subjecting the digital image signal to signal transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform, then dividing the digital image signal into blocks, and subjecting each of the blocks to orthogonal transform, with using a quantization step-size outputted by the particular apparatus and a mean value LM of the amplitude values of pixels in the digital image signal at the time of output, the steps of:
calculating a mean value LMxe2x80x2 of the amplitude values of the pixels in the digital image signal at the time of input, and subtracting a difference DM (=LMxe2x80x2xe2x88x92LM) between the mean value LMxe2x80x2 and the mean value LM from the values of all the pixels in the digital image signal;
dividing the digital image signal after the subtraction of the difference DL into a plurality of blocks each composed of a plurality of pixels previously determined, and subjecting, for each of the blocks, the block to orthogonal transform, to calculate transform coefficients;
further classifying the plurality of blocks obtained by the division into groups each comprising one or two or more blocks in accordance with a previously determined number of blocks;
calculating for each of the groups a mean value of the respective transform coefficients having the lowest frequency components in the blocks belonging to the group, and subjecting the mean value to linear quantization using the previously determined quantization step-size, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
A seventy-ninth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising, with respect to a digital image signal having inherent digital information embedded by a particular apparatus in a mean value of pixels composing each of blocks obtained by dividing the digital image signal, with using a quantization step-size outputted by the particular apparatus, the steps of:
dividing the digital image signal into a plurality of blocks each composed of a plurality of pixels previously determined;
calculating for each of the blocks a mean value of the pixels composing the block, and subjecting the mean value to linear quantization using the quantization step-size, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
An eightieth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising, with respect to a digital image signal having inherent digital information embedded by a particular apparatus in a mean value of pixels composing each of blocks obtained by dividing the digital image signal, with using a quantization step-size and a mean value LM of the amplitude values of the pixels in the digital image signal at the time of output, the steps of
calculating a mean value LMxe2x80x2 of the amplitude values of the pixels in the digital image signal at the time of input, and subtracting a difference DL (=LMxe2x80x2xe2x88x92LM) between the mean value LMxe2x80x2 and the mean value LM from the values of all the pixels in the digital image signal;
dividing the digital image signal after the subtraction of the difference DL into a plurality of blocks each composed of a plurality of pixels previously determined;
calculating a mean value of the pixels composing each of the blocks obtained by the division, and subjecting the mean value to linear quantization using the quantization step-size, to calculate a quantization value; and
judging whether the quantization value is even or odd, to extract the embedded digital information on the basis of the results of the judgment.
An eighty-first aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising the steps of:
dividing a digital image signal into a plurality of frequency bands to obtain transform coefficients using either discrete wavelet transform or sub-band division;
generating, with respect to each of the transform coefficients included in the one or two frequency bands out of the plurality of frequency bands obtained by the division, map information storing a true/false value based on decision whether or not all the absolute amplitude values of the transform coefficient and the other transform coefficients in the same space representation region in the same direction of division as the one or two frequency bands are not more than a previously determined set value; replacing all of the transform coefficient and the other transform coefficients which correspond to the position where the true/false value of the map information is true with a previously determined transform value on the basis of the value of the digital information to be embedded in the transform coefficients; and synthesizing the plurality of transform coefficients after the replacement, to reconstruct a digital image signal.
An eighty-second aspect is characterized in that in the eighty-first aspect,
the transform value is set to integers xc2x1K which are not more than the set value, and
the replacing step replaces the transform coefficient and the other transform coefficients with the transform value +K when each of bits composing the digital information takes a logical value 1, while replacing the transform coefficients with the transform value xe2x88x92K when the bit takes a logical value 0.
An eighty-third aspect is characterized in that in the eighty-first aspect,
the generating step generates the map information with respect to the transform coefficients included in at least one or both of the frequency band which is low in its horizontal component and is high in its vertical component and the frequency band which is high in its horizontal component and is low in its vertical component.
An eighty-fourth aspect is characterized in that in the eighty-second aspect,
the generating step generates the map information with respect to the transform coefficients included in at least one or both of the frequency band which is low in its horizontal component and is high in its vertical component and the frequency band which is high in its horizontal component and is low in its vertical component.
An eighty-fifth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising the steps of:
dividing a digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
generating, with respect to each of the transform coefficients included in the one or two frequency bands out of the plurality of frequency bands obtained by the division, map information storing a true/false value based on decision whether or not the absolute amplitude value of the transform coefficient is included between upper-limit and lower-limit threshold values which are previously determined;
replacing the transform coefficient corresponding to the position where the true/false value of the map information is true with a previously determined transform value on the basis of the sign of the transform coefficient and the value of the digital information to be embedded in the transform coefficient; and
synthesizing the plurality of transform coefficients after the replacement, to reconstruct a digital image signal.
An eighty-sixth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising the steps of:
dividing a digital image signal into a plurality of block signals of a previously determined size, and subjecting, for each of the block signals, the block signal to orthogonal transform, to calculate transform coefficients;
generating, with respect to each of the transform coefficients included in the one or two block signals out of the plurality of block signals obtained by the division, map information storing a true/false value based on decision whether or not the absolute amplitude value of the transform coefficient is included between upper-limit and lower-limit threshold values which are previously determined;
replacing the transform coefficient corresponding to the position where the true/false value of the map information is true with a previously determined transform value on the basis of the sign of the transform coefficient and the value of the digital information to be embedded in the transform coefficient; and
subjecting the plurality of transform coefficients after the replacement to inverse orthogonal transform, to reconstruct a digital image signal.
An eighty-seventh aspect is characterized in that in the eighty-sixth aspect,
the calculating step performs frequency transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform.
An eighty-eighth aspect is characterized in that in the eighty-fifth aspect,
the transform value is set to integers xc2x1A and xc2x1B between the upper-limit and lower-limit threshold values, and
the replacing step replaces the transform coefficient with the transform value +A when each of bits composing the digital information takes a logical value 1 and the sign of the transform coefficient is positive, with the transform value xe2x88x92A when the bit takes a logical value 1 and the sign of the transform coefficient is negative, with the transform value +B when the bit takes a logical value 0 and the sign of the transform coefficient is positive, and with the transform value xe2x88x92B when the bit takes a logical value 0 and the sign of the transform coefficient is negative.
An eighty-ninth aspect is characterized in that in the eighty-sixth aspect,
the transform value is set to integers xc2x1A and xc2x1B between the upper-limit and lower-limit threshold values, and
the replacing step replaces the transform coefficient with the transform value +A when each of bits composing the digital information takes a logical value 1 and the sign of the transform coefficient is positive, with the transform value xe2x88x92A when the bit takes a logical value 1 and the sign of the transform coefficient is negative, with the transform value +B when the bit takes a logical value 0 and the sign of the transform coefficient is positive, and with the transform value xe2x88x92B when the bit takes a logical value 0 and the sign of the transform coefficient is negative.
A ninetieth aspect is characterized in that in the eighty-seventh aspect,
the transform value is set to integers xc2x1A and xc2x1B between the upper-limit and lower-limit threshold values, and
the replacing step replaces the transform coefficient with the transform value +A when each of bits composing the digital information takes a logical value 1 and the sign of the transform coefficient is positive, with the transform value xe2x88x92A when the bit takes a logical value 1 and the sign of the transform coefficient is negative, with the transform value +B when the bit takes a logical value 0 and the sign of the transform coefficient is positive, and with the transform value xe2x88x92B when the bit takes a logical value 0 and the sign of the transform coefficient is negative.
A ninety-first aspect is characterized in that in the eighty-fifth aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A ninety-second aspect is characterized in that in the eighty-sixth aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A ninety-third aspect is characterized in that in the eighty-seventh aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A ninety-fourth aspect is characterized in that in the eighty-eighth aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A ninety-fifth aspect is characterized in that in the eighty-ninth aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A ninety-sixth aspect is characterized in that in the ninetieth aspect,
the generating step generates the map information with respect to the respective transform coefficients having the low frequency components other than the DC components.
A ninety-seventh aspect is directed to a recording medium having a program executed in a computer, the program realizing on the computer an operational environment comprising, with respect to a digital image signal having inherent digital information embedded by a particular apparatus in transform coefficients obtained by dividing the digital image signal using either discrete wavelet transform or sub-band division, with using map information outputted by the particular apparatus and representing the position where the digital information is embedded, the steps of:
dividing the digital image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
extracting, on the basis of the map information, the transform coefficient corresponding to the position where a true/false value of the map information is true and the other transform coefficients in the same space representation region in the same direction of division as the frequency band including the transform coefficient;
calculating a total value of the transform coefficients included in the one or two or more frequency bands out of the transform coefficient and the other transform coefficients which are extracted; and
judging the sign of the total value, to extract the embedded digital information on the basis of the results of the judgment.
A ninety-eighth aspect is directed to a recording medium having a program executed in a computer recorded thereon, the program realizing on the computer an operational environment comprising, with respect to a digital image signal having inherent digital information embedded by a particular apparatus in transform coefficients obtained by dividing the digital image signal using either discrete wavelet transform or sub-band division, with using map information outputted by the particular apparatus and representing the position where the digital information is embedded and information representing a transform value to be embedded, the steps of:
dividing the image signal into transform coefficients over a plurality of frequency bands using either discrete wavelet transform or sub-band division;
extracting, on the basis of the map information, the transform coefficient corresponding to the position where a true/false value of the map information is true;
calculating an absolute error between the extracted transform coefficient and the transform value; and
judging the absolute error, to extract the embedded digital information on the basis of the results of the judgment.
A ninety-ninth aspect is directed to a recording medium having a program executed in a computer, the program realizing on the computer an operational environment comprising, with respect to a digital image signal having inherent digital information embedded by a particular apparatus in transform coefficients obtained by subjecting the digital image signal to frequency transformation which is any one of discrete cosine transform, Fourier transform and Hadamard transform, then dividing the digital image signal into blocks, and subjecting each of the blocks to orthogonal transform, with using map information outputted by the particular apparatus and representing the position where the digital information is embedded and information representing a transform value to be embedded, the steps of:
dividing the digital image signal into a plurality of block signals of a previously determined size, and subjecting, for each of the block signals, the block signal to orthogonal transform, to calculate transform coefficients;
extracting, on the basis of the map information, the transform coefficient corresponding to the position where a true/false value of the map information is true;
calculating an absolute error between the extracted transform coefficient and the transform value; and
judging the absolute error, to extract the embedded digital information on the basis of the results of the judgment.
As described in the foregoing, the sixty-seventh to ninety-ninth aspects are directed to the recording mediums respectively having programs for carrying out digital information embedding and extracting methods in the foregoing forty-fifth to sixty-sixth aspects. This corresponds to the supply of the digital information embedding and extracting methods in the forty-fifth to sixty-sixth aspects to the existing apparatus in the form of software.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.